Studies of adult males with severe developmental dyslexia are underway. A sample of 14 dyslexic men has been identified with a battery of academic and intelligence tests and interviews. Six matched normal controls have also been identified and others are being recruited. Subjects are being studied with EEG spectral analysis combined with topographic mapping and with xenoninhalation procedures for the measurement of regional cerebral blood flow. Lateralizing tasks are being used in conjunction with these procedures. In addition, these subjects have also been characterized as dyslexic with or without attention deficit disorder and are being studied with an extensive battery of event-related potentials (ERPS) designed to differentially assess the ability to initiate, select, inhibit, shift, and sustain attention. Magnetic resonance imaging (MRI) is being used to examine brain anatomy. Other aspects include quantitative neurological examinations for soft signs and neuropsychological testing. We anticipate completing these studies by early 1986 and proceeding to study subgroups of learning disabled children with many of the same methodologies. Thus, additional preparations (with respect to recruiting and test materials) are also underway. Other projects include a series of studies of autistic adults. These include studies of brain anatomy with volumetric CT measures, studies of glucose metabolism with PET, autonomic nervous system studies, psychiatric, and neuropsychological studies. Additional PET-scans on autistic adults are still in progress and will provide a sample size adequate to apply intercorrelational analyses to examine metabolic patterns throughout the brain.